Biological, pathological and clinical features of small cell lung cancer.

Small cell lung cancer, which is not uncommon, and is one of the most malignant and relatively well investigated solid tumors of adults, has been reviewed concerning its biology, pathology and clinical aspects. Although it is histologically very simple, its poorly differentiated epithelial cell characteristics are complicated by features of neuroendocrine cells, such as amine and peptide hormone production and specific enzyme activities, some of which have been found to be good monitoring markers during and after treatment. Because of the relative ease of establishing cell lines in vitro, cell characteristics have been studied in detail. This has led to subtyping of cell lines and may further lead to subtyping of histology. However, accumulation of further evidence has disclosed exceptions and unclassifiable cell lines. The same can be said about chromosomal abnormality. The reactivity of monoclonal antibodies and also oncogenes supports the prevalent concept discriminating small cell cancer from non-small cell cancer. However, concepts concerning histogenesis are still changing. Although it is one of the solid tumors most sensitive to radiation and chemotherapy, the response rate of the tumor to non-surgical treatment appears to have reached a plateau. In order to make a breakthrough in the treatment, strategies based on biological findings must be applied.